Riboflavin

A B vitamin, also called vitamin B2, that forms two coenzymes needed for energy production, growth and the metabolism of fats and drugs. Milk, eggs and meat are rich sources.

How much you need

The official Recommended Dietary Allowance for adults, per day:

Age	Men	Women	Pregnancy	Breastfeeding
19–50 years	1.3 mg	1.1 mg	1.4 mg	1.6 mg
51–70 years	1.3 mg	1.1 mg	—	—
Over 70	1.3 mg	1.1 mg	—	—

People aged 18 fall in the official 14–18 group — 1.3 mg a day for males and 1.0 mg for females, 1.4 mg in pregnancy and 1.6 mg when breastfeeding. There is no upper limit at any age. Pregnancy and breastfeeding change what you need — confirm yours with your midwife, obstetrician or doctor.

Upper limit

No upper limit has been set for riboflavin, because no harm has been reported from high intakes from food or supplements, including 400 mg a day for at least 3 months. The Food and Nutrition Board says that limited data do not prove high intakes are harmless, and urges caution about excessive amounts.

What it does

Riboflavin, also called vitamin B2, is an essential part of two coenzymes, FMN and FAD, which play major roles in energy production; in cell function, growth and development; and in the metabolism of fats, drugs and steroids ^[1]. FAD is needed to convert tryptophan to niacin, and FMN to convert vitamin B6 into its active form ^[1]. Riboflavin also helps keep blood homocysteine at normal levels ^[1].

Forms

More than 90% of the riboflavin in food is in the form of FAD or FMN, although the main form in eggs and milk is free riboflavin ^[1]. In most supplements it is in the free form; multivitamins commonly provide 1.3 mg ^[1].

Where it comes from

Beef liver, pan fried3 ounces2.9 mg
Breakfast cereals, fortified with 100% of the Daily Value for riboflavinfortified1 serving1.3 mg
Oats, instant, fortified, cooked with waterfortified1 cup1.1 mg
Yogurt, plain, fat free1 cup0.6 mg
Milk, 2% fat1 cup0.5 mg

How these five were chosen: The five foods with the most riboflavin per serving in the NIH fact sheet's food table. Fortified foods are marked.

How far one serving goes toward a day's riboflavin

How far one serving goes toward a day's riboflavin
Item	Percent of the adult daily amount (1.3 mg)
Beef liver	223%
Breakfast cereal	100%
Oats, instant	85%
Yogurt, fat free	46%
Milk, 2%	38%

Against the recommended daily amount for adults 19 to 50: 1.3 mg, the highest value for men or women in that age range. Where a food varies by brand, the bar shows the lowest figure and the label the full range. Computed from the figures on this page, taken from the NIH fact sheet.

Getting the most from it

About 95% of the riboflavin in food is absorbed, up to about 27 mg per meal or dose ^[1]. Boiling loses about twice as much as steaming or microwaving, because riboflavin dissolves in the cooking water ^[1]. Light rapidly breaks it down, which is why milk is not usually sold in glass ^[1].

In the United States

Most Americans get enough riboflavin: in 2003–2006 data, fewer than 6% had intakes from food and supplements below the average requirement ^[1]. Adults average 2.5 mg a day from food for men and 1.8 mg for women, and 4.5 mg and 4.7 mg including supplements ^[1]. Milk and milk drinks, bread, meat dishes, ready-to-eat cereals and grain dishes are the largest sources, and grains and cereals are fortified with riboflavin in the United States ^[1].

Who is most likely to run low

Vegetarian athletes — exercise increases the need, and some vegetarians avoid milk, yogurt, cheese and eggs, good sources of riboflavin ^[1]
Pregnant or breastfeeding women who rarely eat meat or dairy products, including some vegetarians in the United States ^[1]
People who are vegan or consume little milk ^[1]
People with riboflavin transporter deficiency, a rare neurological disorder that prevents riboflavin from being absorbed and transported ^[1]

What deficiency looks like

Deficiency is extremely rare in the United States ^[1]. Its signs include skin disorders, redness and swelling of the mouth and throat, sores at the corners of the mouth, swollen and cracked lips, hair loss, reproductive problems, sore throat, itchy red eyes and degeneration of the liver and nervous system ^[1]. Because people with riboflavin deficiency usually lack other nutrients too, some of these signs may come from those ^[1]. Severe, prolonged deficiency can cause anemia and cataracts; early changes are easily reversed, but later ones, such as cataracts, rarely are ^[1].

What the evidence supports, and what it doesn't

Established. Riboflavin is essential for the coenzymes FMN and FAD, which energy production and the metabolism of other B vitamins depend on; severe deficiency impairs the metabolism of other nutrients ^[1]. In riboflavin transporter deficiency, high-dose riboflavin can be a life-saving treatment, especially when started soon after symptoms begin ^[1].

Not supported by trials. Cancer prevention: data are limited and findings mixed — large observational studies disagree on lung and colorectal cancer, and the fact sheet says clinical trials are needed to find out whether supplements reduce cancer risk ^[1].

Mixed. Migraine: in a trial in 55 adults with migraine, 400 mg a day reduced attacks by two a month compared with placebo, but two small trials in children found that 50 to 200 mg a day did not reduce headaches ^[1]. The American Academy of Neurology and the American Headache Society concluded that riboflavin is probably effective for preventing migraine, and the Canadian Headache Society recommends it while calling the evidence low quality ^[1].

Too much

Intakes from food many times the recommended amount show no toxicity, possibly because riboflavin is poorly soluble and its absorption is limited ^[1]. No harm has been reported from 400 mg a day for at least 3 months, although the Food and Nutrition Board urges caution about excessive amounts ^[1].

Medicines that interact

Riboflavin is not known to have any clinically relevant interactions with medicines ^[1]. If you take medicines regularly, your doctor or pharmacist can still tell you whether any supplement suits you.